Method for preparing storage-stable fast-drying multi-component aqueous coating compositions and coatings derived therefrom

ABSTRACT

A storage stable, fast drying multi-component aqueous coating composition which includes an anionically stabilized binder polymer, a vinylamine polymer and a volatile base is disclosed. A method for using the aqueous coating composition to produce a coating on the surface of a substrate is further disclosed, along with the coating produced.

This application is a divisional of prior U.S. application Ser. No.10/095,365, filed Mar. 11, 2002 now U.S. Pat. No. 6,734,226.

The present invention relates to storage-stable fast-dryingmulti-component aqueous coating compositions and fast-drying coatingsmade therefrom.

Used herein, the term “multi-component” refers to aqueous coatingcompositions having two or more components applied to a substrate in oneor more steps.

One of the many important features of coating compositions is the speedat which they dry on the surface of a given substrate after application.For instance, the drying speed of a traffic paint dictates the length ofthe period of disruption to road traffic during application of thatpaint to road surfaces, and subsequent drying. The trend is to demandshorter and shorter disruptions of traffic flow, and to meet this demandby using faster drying coating compositions.

Solvent-based fast-drying coating compositions are based on organicpolymeric binders dissolved, suspended or otherwise dispersed inrelatively low-boiling organic solvents. Low-boiling volatile organicsolvents evaporate rapidly after application of the coating compositionon the road to provide the desired fast drying characteristics of afreshly applied road marking. However, in addition to releasing volatileorganic solvents into the environment, this type of paint formulationtends to expose workers to the vapors of the organic solvents. Becauseof these shortcomings and increasingly stringent environmental mandatesfrom governments and communities, it is highly desirable to develop moreenvironmentally friendly coating compositions while retaining fastdrying properties and/or characteristics.

A more environmentally friendly coating composition uses water based,i.e., aqueous, rather than solvent based, polymers or resins. Coatingformulations, both solvent based and aqueous, include binders. The terms“binder” and “binder polymer” used herein refer to polymers that areincluded in the coating composition and that participate in filmformation, becoming part of the resultant film. Binder polymerstypically have glass transition temperature (Tg) values in the range−10° C. to 70° C. because those having Tg values below −10° C. tend tohave poor resistance to dirt pick-up and those having Tg values above70° C. usually display diminished ability to form films. In certainapplications, however, the lower limit for Tg can be even lower than−10° C. For example, the binder polymers used in roof coatings can haveglass transition temperatures as low as −40° C. Primarily due to acombination of high boiling point, high latent heat of vaporization,high polarity, and strong hydrogen bonding of water, drying times of thecoatings formed by application of an aqueous coating composition to asubstrate surface are generally longer than those exhibited by theorganic solvent based coatings. The drying time strongly depends on therelative humidity of the atmosphere in which the coating compositionsare applied. An aqueous coating composition may take several hours ormore to dry in high humidity. The problem of retarded drying rate isespecially aggravated for thick film (greater than about 500μ) coatings.Long drying times severely limit the desirability of using aqueouscoating compositions, particularly traffic paints, the drying times ofwhich directly effect the length of traffic disruptions.

U.S. Pat. No. 5,804,627 discloses methods of producing fast dryingcoatings on the surfaces of substrates. The methods include applying tothose surfaces an aqueous coating composition including an anionicallystabilized emulsion polymer having a Tg greater than about 0° C., apolyamine functional polymer having from about 20% to about 100% of themonomer units by weight containing an amine group, and an amount ofvolatile base sufficient to raise the pH of the composition to a pointwhere essentially all of the polyamine functional polymer is in anon-ionic state. During and after application of the aqueous coatingcomposition to the surface of a substrate, the volatile base evaporateswith the result that the anionically stabilized polymer particles aredestabilized by protonated polyamine functional polymer, therebyaccelerating the drying rate of the coating. Although this systemaffords improvement in drying speeds, more efficient polyaminefunctional polymers are desired, imparting, for example, equivalentdrying speed at reduced levels in coating compositions.

WO 96/22338 discloses a fast drying aqueous coating composition whichderives its fast drying characteristic from a mechanism similar to thatof U.S. Pat. No. 5,804,627, except that the polyamine functional polymeris poly(ethyleneimine), also referred to herein as PEI. PEI is formed bypolymerization of ethylene imine, a highly carcinogenic monomer. Thenitrogen content of PEI is higher than that of the other conventionalpolyamine functional polymers, and this higher nitrogen content offeredthe promise of higher drying efficiency. Unfortunately, the highlycarcinogenic ethylene imine may be present, to some extent, in coatingcompositions containing PEI, so that such compositions are to be avoidedfor environmental reasons. Extensive steps must also be taken duringmanufacture of PEI to prevent exposure of workers to ethylene imine.Moreover, although the promise of PEI in fast drying aqueous coatingcompositions is that its high level of nitrogen, present as amino groupsin the backbone of PEI, will translate into improved drying rates, thatpromise cannot be fully realized for at least two reasons. First, as thevolatile base evaporates from the coating, acidic substances becomeavailable to react with the amino groups, yet a significant portion ofthose backbone amino groups will be less basic and be less accessible tothe acidic substances due to the high degree of steric hindrance fromadjacent portions of the backbone of the polymer. As a result, theformation of ammonium ions, an essential step in the destabilization ofthe coating composition, does not occur for all of the amino groups ofPEI. Second, and perhaps more importantly, a substantial portion of theammonium groups that do form from such reaction are not fully accessiblefor interaction with, and subsequent destabilization of, anionicallystabilized emulsion polymers.

We have, surprisingly, found that vinylamine polymers are highlyefficient at producing storage stable, fast-drying aqueous coatingcompositions when those compositions include anionically stabilizedbinder polymer and volatile base. Unlike the amino groups of PEI, theamino groups of vinylamine polymers are fully available for protonationafter evaporation of the volatile amine with the result that vinylaminepolymers are more efficient (i.e., give more rapid drying at equalconcentrations) than PEI in spite of equal nitrogen content.

One aspect of the present invention relates to a storage stable, fastdrying aqueous coating composition, said composition comprising:

-   -   (a) an anionically stabilized binder polymer;    -   (b) a vinylamine polymer having from 20% to 100% by weight of        amine functional units, based on total weight of said vinylamine        polymer; and    -   (c) an amount of volatile base sufficient to raise the pH of        said composition to a point where essentially all of the amine        groups of said vinylamine polymer are in a non-ionic state.

A second aspect of the present invention relates to a coating on thesurface of a substrate, said coating comprising:

-   -   (a) an anionically stabilized binder polymer; and    -   (b) a vinylamine polymer having from 20% to 100% by weight of        amine functional units, based on total weight of said vinylamine        polymer.

A third aspect of the present invention relates to a method of producinga coating on the surface of a substrate, said method comprising thesteps of:

-   -   (i) applying to said surface a fast drying aqueous coating        composition comprising:        -   (a) an anionically stabilized binder polymer;        -   (b) a vinylamine polymer having from 20% to 100% by weight            of amine functional units, based on total weight of said            vinylamine polymer; and        -   (c) an amount of volatile base sufficient to raise the pH of            said composition to a point where essentially all of the            amine groups of said vinylamine polymer are in a non-ionic            state;    -   (ii) evaporating said volatile base from said composition; and    -   (iii) drying said composition to form said coating.

A fourth aspect of the present invention relates to a method ofproducing a coating on the surface of a substrate, said methodcomprising the steps of:

-   -   (i) applying to said surface an aqueous composition comprising        an anionically stabilized binder polymer;    -   (ii) applying to said surface an aqueous composition comprising        a vinylamine polymer having from 20% to 100% by weight of amine        functional units, based on total weight of said vinylamine        polymer; and    -   (iii) drying said coating.

The method of the fourth aspect of the present invention may furtherinclude, in the aqueous composition comprising a vinylamine polymer, avolatile base in an amount sufficient to deprotonate 20% to 100% of theamine groups of the vinylamine polymer. When the volatile base ispresent in the aqueous composition comprising a vinylamine polymer, themethod further includes the step of evaporating the volatile base fromthe coating.

Additional aspects of the present invention include the composition ofthe first aspect and the method of the third aspect wherein the amountof volatile base is sufficient to deprotonate 20% to 100% of the aminegroups of said vinylamine polymer.

Used herein, the following terms have these definitions:

“Multi-component” refers to coating compositions having two or morecomponents which may be applied to a substrate in one or more steps, andto the coatings made thereby.

The term “roadway” is used herein as a generic term and it includes anyindoor or outdoor solid surface that is or may be exposed topedestrians, moving vehicles, tractors, or aircraft continuously,continually, or intermittently. Some non-limiting examples of a“roadway” include highways, streets, driveways, sidewalks, runways,taxiing areas, tarmac areas, parking lots, rooftops, and indoor floors(such as factory floors, or floors inside shopping malls). The surfacematerial may be masonry, tar, asphalt, resins, concrete, cement, stone,stucco, tiles, wood, polymeric materials and combinations thereof. Usedherein, the term “roadway” also embraces any surface of any substrateassociated with a roadway, including, for example, signs, barricades,medial strips, and signal devices.

A “roadway marking” is a coating on the surface of a “roadway”.

A “traffic paint” is a coating composition used to form a roadwaymarking. The traffic paints of the present invention are multi-componentaqueous coating compositions.

“Tg” is the “glass transition temperature” of a polymeric phase. Theglass transition temperature of a polymer is the temperature at which apolymer transitions from a rigid, glassy state at temperatures below Tgto a fluid or rubbery state at temperatures above Tg. The Tg of apolymer is typically measured by differential scanning calorimetry (DSC)using the mid-point in the heat flow versus temperature transition asthe Tg value. A typical heating rate for the DSC measurement is 20°C./minute. The Tg of various homopolymers may be found, for example, inPolymer Handbook, edited by J. Brandrup and E. H. Immergut, IntersciencePublishers. The Tg of a polymer is calculated by using the Fox equation(T. G. Fox, Bull. Am. Physics Soc., Volume 1, Issue No. 3, page 123(1956)).

The term “fast-drying” is used herein to mean that a film (i.e., thecoating) of a so designated coating composition having a wet coatingthickness of 330 microns displays a dry-through time of less than twohours at 90% relative humidity at 23° C. The term “fast-drying aqueousbinder composition” refers to an aqueous dispersion of at least onebinder polymer that, when applied to a substrate, forms a coating havinga dry-through time conforming to the definition of “fast-drying” justgiven.

The term “amino group” refers to a functional group containing one ormore amine nitrogen atoms, wherein an amine nitrogen atom is a nitrogenatom bearing three substituents (e.g., hydrogen, or alkyl, or a portionof a polymer backbone) and a lone pair of electrons. The term “aminegroup” is used interchangeably with “amino group”.

The term “ammonium group” refers to a functional group containing one ormore ammonium nitrogen atoms, wherein an ammonium nitrogen atom is anitrogen atom bearing four substituents (e.g., hydrogen, or alkyl, or aportion of a polymer backbone) and having a positive charge. Theammonium nitrogen atom, along with the substituents attached to it isalso referred to as an “ammonium ion”

“Vinylamine polymer” refers to the unsubstituted “poly(vinylamine)homopolymer”, and is abbreviated “PVAm”. PVAm copolymers are also usefulin the present invention, as are N-substituted PVAm homopolymers andcopolymers, and N,N-disubstituted PVAm homopolymers and copolymers.

The “backbone” of a polymer chain is a collection of atoms wherein eachatom is directly attached to at least two other atoms that form theactual links of the polymer chain. “Terminal” atoms of the backbone arethe only exception in that they are connected to only one other atomthat forms an actual link of the polymer chain. For example, whenethylene imine is polymerized, its nitrogen and both of its carbonsbecome part of the backbone of the polymer that is produced.

A “linear” polymer is a polymer having a backbone that is not branched.

A “branched” polymer is a polymer having a backbone that has otherbackbone segments (i.e., “branches”) attached to it. For example, thetertiary nitrogens of PEI serve as points of attachment (i.e., “branchpoints”) for other backbone segments.

A “pendant” group is a group that is attached to the backbone of apolymer, yet is not part of that backbone. For example, thepoly(vinylamine) backbone contains the two carbons of the vinylaminemonomer unit, but the amino group, —NH₂, of the vinylamine unit is apendant group. The amino group is said to be “pendant to” the backboneof the polymer.

“Molecular Weight” may be defined in several ways. Synthetic polymersare almost always a mixture of many different molecular weights, i.e.there is a “molecular weight distribution”, abbreviated “MWD”. For ahomopolymer, members of the distribution differ in the number of monomerunits which they contain. This idea also extends to copolymers. Giventhat there is a distribution of molecular weights, the most completecharacterization of the molecular weight of a given sample is thedetermination of the entire molecular weight distribution. Thischaracterization is obtained by separating the members of thedistribution and then quantitating the amount of each that is present.Once this distribution is at hand, there are several summary statistics,or moments, which can be generated from it to characterize the molecularweight of the polymer.

The two most common moments of the distribution are the “weight averagemolecular weight”, “M_(w)”, and the “number average molecular weight”,“M_(n)”. These are defined as follows:M _(w)=Σ(W _(i) M _(i))/ΣW _(i)=Σ(N _(i) M _(i) ²)/ΣN _(i) M _(i)M _(n) =ΣW _(i)/Σ(W _(i) /M _(i))=Σ(N _(i) M _(i))/ΣN _(i)where:

M_(i)=molar mass of i^(th) component of distribution

W_(i)=weight of i^(th) component of distribution

N_(i)=number of chains of i^(th) component

and the summations are over all the components in the distribution.M_(w) and M_(n) are typically computed from the MWD as measured by GelPermeation Chromatography (see the Experimental Section).

The present invention requires that the aqueous coating compositioninclude as components a vinylamine polymer and an anionically stabilizedemulsion polymer. Additionally, a volatile base is included at aconcentration sufficient to deprotonate the conjugate acid of the aminogroups of the vinylamine polymer. Typically, 20 to 100 mole % of theamino groups of the vinylamine polymer are deprotonated, preferably 60to 100 mole %, more preferably 80 to 100 mole %, and most preferably 90to 100 mole %. The presence of the vinylamine polymer in deprotonatedform is necessary if the coating composition is to remain stable duringstorage, shipping, and handling. The deprotonated amino groups do notbear a charge and, as such, do not interact with the anionic surfactantused to stabilize the emulsion polymer. Once the aqueous coatingcomposition is applied to the surface of a substrate, the volatile baseevaporates from the coating. As the volatile base escapes, the aminogroups of the vinylamine polymer become protonated to form a conjugatebase which is an ammonium cation. The resultant cationic vinylaminepolymer then interacts with the anionic surfactant to destabilize theemulsion polymer and, as a result, the coating composition. In that way,accelerated drying is achieved. In the present invention, typically, 5to 100 mole % of the amino groups of the vinylamine polymer becomeprotonated, forming ammonium groups, as the volatile base evaporatesfrom the aqueous coating composition as it dries on the substratesurface to become a coating. Preferably the percent of amino groups ofthe vinylamine polymer that become protonated is 10 to 100 mole %, morepreferably 40 to 100 mole %, and most preferably 80 to 100 mole %.

The vinylamine polymers of the present invention are unique polyaminefunctional polymers. Conventional polyamine functional polymers known tothe art include, for example, aminoalky vinyl ethers and sulfides;(meth)acrylamides and (meth)acrylic esters, such as dimethylaminoethyl(meth)acrylate, bearing amine functionality; and PEI. Poly(vinylamine)homopolymer, PVAm, itself is higher in nitrogen content than allconventional polyamine functional polymers, with the exception of PEI,which has the same nitrogen content. Although PVAm and PEI have the samenumber of amino groups, the amino groups of PVAm are primary aminegroups and, as such, are less sterically hindered, and more readilyaccessible than those of PEI, with the result that protonated PVAm ismore efficient at destabilizing the anionic emulsion polymer toaccelerate drying. Upon application of the coating composition to thesurface of a substrate, the volatile amine evaporates, and the aminegroups of poly(vinylamine) homopolymer become protonated to formammonium salts. Due to its higher nitrogen content, the protonated pVAmthus formed has a higher charge density than conventional polyaminefunctional polymers. This higher charge density translates into higherefficiency when the protonated poly(vinylamine) homopolymer interactswith the centers of negative charge on the anionic surfactants. As aresult, destabilization of a given anionically stabilized latex may beachieved with reduced levels of pVAm. Further, this enhanced efficiencyis conferred to N-substituted and N,N-disubstituted vinylamine polymerswhen compared with other polyamine functional polymers having identicalsubstituents on nitrogen, and to vinylamine copolymers (co-pVAms) whencompared to other polyamine functional co-polymers having identicallevels of co-monomer present as polymerized units.

Only one other polyamine functional polymer offers a nitrogen content ashigh as that of poly(vinylamine). That polymer is poly(ethylene imine),referred to herein as PEI. PEI is formed by the polymerization ofethylene imine, a highly carcinogenic monomer. Ethylene imine may,therefore, be present, to some extent, in coating compositionscontaining PEI, so that such compositions are to be avoided forenvironmental reasons. Moreover, there exist several importantstructural distinctions between the amino groups of PVAm and those ofPEI. When ethylene imine monomer reacts to form PEI, its nitrogen groupbecomes an integral part of the polymer backbone. In linear portions ofthe PEI backbone (i.e., portions where branching has not occurred) therepeat unit is —CH₂—CH₂—NH—, and a segment of the PEI backbonecontaining, for example, three of these linear repeat units has thisstructure:—CH₂—CH₂—NH—CH₂—CH₂—NH—CH₂—CH₂—NH—.

Because each amine nitrogen of PEI is part of the backbone of the PEIpolymer, each amine nitrogen has attached to it either one (i.e., whenthe amino group occurs at the terminus of the backbone), two (secondaryamino groups, i.e., neither a terminus, nor a branch point), or three(tertiary amino groups occurring as branch points) long substituents,each of which is a segment of polymer backbone. This situation isrepeated for every nitrogen imbedded in the PEI backbone. For most ofthe amine nitrogen atoms of the PEI backbone, these substituents may bea few, or tens, or hundreds of atoms long. It is well known in the artof amine chemistry that multiple bulky substituents on the nitrogen ofan amine reduce the reactivity of the lone pair of electrons on thatnitrogen due to steric hindrance (see D. Barton and W. D. Ollis,Comprehensive Organic Chemistry, vol. 2, pp. 34-36, Pergamon Press, NewYork, 1979). The space immediately surrounding the nitrogen loneelectron pair becomes so crowded that the amino group is hindered frominteracting with other chemical entities, and in fact the electrondensity of the lone electron pair decreases as the geometry around thenitrogen becomes flattened due this crowding. For the PEI amine nitrogenatoms, the steric hindrance provided by the two or three extremely largesubstituents may impede even interaction with small chemical entities,including the proton. It is, therefore, difficult to protonate all, oralmost all of the amino groups imbedded in the PEI backbone, so that thehigh nitrogen content of PEI is not matched by a similarly high chargedensity (i.e., ammonium groups) once the volatile amine has evaporatedfrom the coating. Furthermore, those amino groups that are protonated toform positively charged ammonium groups have reduced interaction withother chemical entities, again due to very high steric hindranceafforded by the bulky substituent groups.

In order to destabilize the anionically stabilized emulsion polymer ofthe coating composition, the highly hindered ammonium groups ofprotonated PEI must make a very close approach to the anionic end of ananionic surfactant molecule which itself is bulky due to the presence ofa large hydrophobic tail. The result is that, for many of the ammoniumgroups that do form along the main chain of protonated PEI, therequisite very close approach is not possible, and those ammonium groupsare unable to participate in deactivating the anionic surfactantmolecules. As if this situation were not bad enough, PEI is actually nota linear polymer. The ratio of primary amino groups to secondary, totertiary is 1:2:1, so that approximately 25% of the nitrogen atoms aresurrounded by three bulky substituents, making those nitrogen atomsparticularly inaccessible as can be seen for the following tertiarynitrogen center:

Titration of PEI in water clearly demonstrates this inaccessibility.Even at the very low pH of 2, only 75% of the nitrogens of PEI (i.e., apercentage equal to the percent of primary and secondary nitrogenspresent) are protonated. This titration data is available in thePolymin™ (Polyethylenimine) product bulletin from BASF.

So, the promise of the high nitrogen content of PEI is not realized as acorrespondingly high number of destabilized anionic surfactantmolecules. Due to extremely high steric hindrance, only a fraction ofthe amino groups can be converted to ammonium groups as the volatilebase evaporates, and many of those ammonium groups that do form areimpeded from contact with anionic surfactant molecules, again due tosteric hindrance. Though not wishing to be bound by any particulartheory, we believe that, by contrast, pVAm is a linear polymer, havingprimary amino groups pendant to its backbone. Because they are primary,all of the nitrogen atoms of the amino groups are fully accessible forprotonation and the ammonium groups that result are fully accessible forinteraction with, and destabilization of anionic surfactants. In short,pVAm is more efficient than PEI, or any other polyamine functionalpolymer, at destabilization of anionically stabilized polymers. Thissuperior efficiency of destabilization leads directly to faster dryingrates for pVAm when compared with other polyfunctional amine polymers atequal weight percent concentration.

The binder polymer of the present invention can be any polymer that caneither be prepared as a dispersion in water, or be dispersed in waterafter preparation. The composition of a binder polymer may be anycomposition that is characterized by a glass transition temperaturefalling in ranges specified herein above in the definition of “binderpolymer”. The specific method by which a binder polymer is prepared isnot of particular importance to the present invention. Binder polymersuseful in the compositions of the present invention may be prepared viabulk or solution polymerization; or by aqueous dispersion, suspension,or emulsion polymerization; or by any other method that would producethe desired polymer dispersed in water, or capable of being dispersed inwater. A preferred method for preparing the binder polymers to be usedin coating composition of the present invention is aqueous emulsionpolymerization. Polymers thus prepared are usually stabilized by addinganionic, nonionic, cationic, or amphoteric surfactants, or by theincorporation of anionic or cationic moieties into the polymer itselfduring synthesis. The emulsion polymerization can be carried out by anumber processes such as those described in Blackley, D. C. EmulsionPolymerisation; Applied Science Publishers: London, 1975; Odian, G.Principles of Polymerization; John Wiley & Sons: New York, 1991;Emulsion Polymerization of Acrylic Monomers; Rohm and Haas, 1967.

The aqueous emulsion polymer preferred as a binder polymer in thepresent invention is an addition polymer. The monomers from which theaddition polymer is formed are ethylenically-unsaturated. The aqueousemulsion polymer composition may be selected and the polymer prepared byconventional techniques known to those of ordinary skill in the art. Thepolymer may contain, as polymerized units, one or more ethylenicallyunsaturated monomers. Examples of these ethylenically unsaturatedmonomers include: C₁-C₂₂ linear or branched chain alkyl (meth)acrylates,bornyl (meth)acrylate, isobornyl (meth)acrylate, and the like;hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate;(meth)acrylamide or substituted (meth)acrylamides; styrene orsubstituted styrenes; butadiene; vinyl acetate or other vinyl ester;butylaminoethyl (meth)acrylate, di(methyl)aminoethyl (meth)acrylate; amonomer containing αβ-unsaturated carbonyl functional groups such asfumarate, maleate, cinnamate and crotonate; and (meth)acrylonitrile.Used herein, the word fragment “(meth)acryl” refers to both “methacryl”and “acryl”. For example, (meth)acrylic acid refers to both methacrylicacid and acrylic acid, and methyl (meth)acrylate refers to both methylmethacrylate and methyl acrylate.

Halocarbon monomers and siloxane monomers may also be used to preparethe binder polymers of the present invention. Halocarbon monomers aremonomers having bromo-, chloro-, or fluoro- sustituents, or combinationsthereof. Halocarbon monomers include, for example: 2-bromoethyl(meth)acrylate; 4-bromostyrene; vinylidene chloride, vinyl chloride;pentafluorophenyl (meth)acrylate; 2-(perfluoroalkyl)ethyl(meth)acrylates, including 2-(perfluorododecyl)ethyl (meth)acrylate, and2-(perfluorohexyl)ethyl (meth)acrylate; tetrafluoroethylene, andvinylidene fluoride.

A acid-functional monomers of the binder polymer of the presentinvention may also be present as polymerized units at preferably 0-10%by weight, based on the weight of the dry emulsion polymer.Acid-functional monomers useful in the present invention include, forexample, (meth)acrylic acid, itaconic acid, crotonic acid, phosphoethyl(meth)acrylate, sulfoethyl (meth)acrylate,2-acrylamido-2-methyl-1-propanesulfonic acid, fumaric acid, maleicanhydride, monomethyl maleate, and maleic acid.

Optionally, a low level of a multi-ethylenically unsaturated monomer maybe incorporated into the polymer to provide crosslinking. The level ofmulti-ethylenically unsaturated monomer may be 0-5% by weight, based onthe weight of the dry emulsion polymer. The upper limit is typicallydetermined by the point at which film formation becomes impaired. Usefulmulti-ethylenically unsaturated monomers include, for example, allyl(meth)acrylate, diallyl phthalate, 1,4-butylene glycol di(meth)acrylate,1,6-hexanediol di(meth)acrylate, and trimethylolpropanetri(methyl)acrylate.

Conventional surfactants may be used to stabilize the emulsionpolymerization systems before, during, and after polymerization ofmonomers. These conventional surfactants will usually be present atlevels of 0.1 percent to 6 percent by weight based on the weight oftotal monomer. At least one anionic, nonionic, or amphoteric surfactantmay be used, or mixtures thereof. Alternatively, all, or a portion, ofthe surfactant activity may be provided by initiator fragments, such asthose of persulfates, when the fragments become incorporated into thepolymer chain. Examples of anionic emulsifiers include sodium laurylsulfate, sodium dodecyl benzene sulfonate, dioctylsulfosuccinate, sodiumpolyoxyethylene lauryl ether sulfate, and sodium salt oftert-octylphenoxyethoxypoly(39)ethoxyethyl sulfate. Examples of nonionicsurfactants include glycerol aliphatic esters, oleic acid monoglyceride,polyoxyethylene aliphatic esters, polyoxyethylene glycol monostearate,polyoxyethylene cetyl ether, polyoxyethylene glycol monolaurate,polyoxyethylene glycol monooleate, polyoxyethylene glycol stearate,polyoxyethylene higher alcohol ethers, polyoxyethylene lauryl ether,polyoxyethylene nonylphenol ether, polyoxyethylene octylphenol ether,polyoxyethylene oleyl ether, polyoxyethylene stearyl ether,polyoxyethylenesorbitan aliphatic esters, polyoxyethylenesorbitanmonolaurate, polyoxyethylenesorbitan monooleate, polyoxyethylenesorbitanmonopalmitate, polyoxyethylenesorbitan monostearate,polyoxyethylenesorbitan trioleate, polyoxyethylenesorbitan tristearate,polyoxyethylenesorbitol tetraoleate, stearic acid monoglyceride,tert-octylphenoxyethylpoly(39)ethoxyethanol, andnonylphenoxyethylpoly(40)ethoxyethanol.

Amphoteric surfactants may also be utilized to stabilize particles ofthe polymer during and after aqueous emulsion polymerization, or otherdispersion polymerizations. For the purpose of stabilizing particles ofpolymer in aqueous systems, amphoteric surfactants may be used at levelsof 0.1 percent to 6 percent by weight based on the weight of totalmonomer. Useful classes of amphoteric surfactant include aminocarboxylicacids, amphoteric imidazoline derivatives, betaines, and macromolecularamphoteric surfactants. Amphoteric surfactants from any of these classesmay be further substituted with fluorocarbon substituents, siloxanesubstituents, or combinations thereof. Useful amphoteric surfactants canbe found in Amphoteric Surfactants, ed. B. R. Bluestein and C. L.Hilton, Surfactant Series Vol. 12 Marcel Dekker NY, N.Y.(1982).

Initiation of emulsion polymerization may be carried out by the thermaldecomposition of free radical precursors, also called initiators herein,which are capable of generating radicals suitable for initiatingaddition polymerization. Suitable thermal initiators such as, forexample, inorganic hydroperoxides, inorganic peroxides, organichydroperoxides, and organic peroxides, are useful at levels of from0.05% to 5.0% by weight, based on the weight of monomers. Free radicalinitiators known in the art of aqueous emulsion polymerization includewater-soluble free radical initiators, such as hydrogen peroxide,tert-butyl peroxide; alkali metal (sodium, potassium or lithium) orammonium persulfate; or mixtures thereof. Such initiators may also becombined with reducing agents to form a redox system. Useful reducingagents include sulfites such as alkali metal meta bisulfite, orhyposulfite, sodium thiosulfate, or sodium formaldehyde sulfoxylate. Thefree radical precursor and reducing agent together, referred to as aredox system herein, may be used at a level of from about 0.01% to 5%,based on the weight of monomers used. Examples of redox systems includet-butyl hydroperoxide/sodium formaldehyde sulfoxylate/Fe(III) andammonium persulfate/sodium bisulfite/sodium hydrosulfite/Fe(III). Thepolymerization temperature may be 10° C. to 110° C., depending upon suchthings as free radical initiator decomposition constant and reactionvessel pressure capabilities.

Frequently, a low level of chain transfer agent such as a mercaptan (forexample: n-octyl mercaptan, n-dodecyl mercaptan, butyl or methylmercaptopropionate, mercaptopropionic acid at 0.05% to 6% by weightbased on total weight of monomer) is employed to limit the formation ofany significant gel fraction or to control molecular weight.

Used herein, the term “vinylamine polymer” refers to poly(vinylamine)homopolymer, vinylamine copolymers, N-substituted poly(vinylamine)homopolymers, N,N-disubstituted poly(vinylamine) homopolymers,N-substituted vinylamine copolymers, N,N-disubstituted vinylaminecopolymers, and combinations thereof. Unsubstituted poly(vinylamine)homopolymer is abbreviated “pVAm”, and is interchangeably referred toherein as “poly(vinylamine)” or “poly(vinylamine) homopolymer”.Vinylamine copolymers may contain one or more types of vinylaminemonomer as polymerized units. Alternatively or additionally, vinylaminecopolymers may include, as polymerized units, monomers that are notvinylamine monomers. PVAm is available as Lupasol™ LU 321 from BASFCorporation, Rensselaer, N.Y. The N-substituents of N-substituted pVAmsand N-substituted vinylamine copolymers, include linear, branched, orcyclic alkyl groups having 1 to 6 carbons, and β-hydroxyalkyl groupshaving 1 to 6 carbons. The vinylamine copolymers must contain vinylaminemonomer, N-substituted vinylamine monomer, N,N-substituted vinylaminemonomer, or combinations thereof, present as polymerized units, in anamount of, preferably 20 to 100 mole percent, more preferably 50 to 100mole %, and most preferably 80 to 100 mole % of the vinylaminecopolymer. All ranges specified herein are inclusive and combinable. TheN-substituents of N,N-disubstituted pVAms and N,N-disubstitutedvinylamine copolymers include linear, branched, or cyclic alkyl groupshaving 1 to 6 carbons, β-hydroxyalkyl groups having 1 to 6 carbons, andcombinations thereof. Preferred vinylamine polymers are poly(vinylamine)homopolymer, poly(N-methylvinylamine), poly(N-ethylvinylamine), andpoly(N-propylvinylamine). Most preferred is poly(vinylamine)homopolymer. The monomers that are not vinylamine monomers, orprecursors to vinylamine functionality such as N-vinylformamide, thatare useful in the preparation of vinylamine copolymers may be any of themonomers listed herein above as useful in the preparation of the binderpolymer.

The vinylamine polymers of the present invention may be, in either theirfully protonated, partially protonated or fully deprotonated forms,insoluble in water. Alternatively, they may be soluble or partiallysoluble in water when present at any degree of protonation. In themethod of the present invention, the vinylamine polymer may be appliedto the surface of a substrate as part of the aqueous coating compositionwhich includes an anionically stabilized binder polymer and a volatilebase. Alternatively, the vinylamine polymer may be applied as acomponent of an aqueous composition that is separate from the aqueouscomposition containing the anionically stabilized binder polymer. In thelatter alternative, a volatile base may, optionally, be present in theaqueous composition containing the vinylamine polymer. Vinylaminepolymers may be prepared in a variety of ways, a few examples of whichare found in the following references. U.S. Pat. No. 5,492,765 disclosespreparation of vinylamine copolymers, for example, copolymerscontaining, as polymerized units, ethylene, vinyl alcohol and vinylaminederived from monomers including vinyl acetate, ethylene,N-vinylformamide, and N-vinylacetamide. The amino groups of theseco-pVAms may be in ammonium ion form due to reaction with mineral acid,or in non-ionic form, or in partially neutralized form, depending uponpH. Weight average molecular weights (Mw) are in the range10,000-500,000. Re. 30,362, a reissue of U.S. Pat. No. 4,018,826,discloses the preparation of pVAm salts of mineral acids fromvinylacetamide. U.S. Pat. No. 4,774,285 discloses N-vinylformamide(95-10 mole %) copolymerized with 5-90 mole % of ethylenicallyunsaturated monomers including: vinyl acetate, vinyl propionate; C1-C4alkyl vinyl ethers; esters, nitriles, and amides of (meth)acrylic acid;(meth)acrylic acid; and N-vinylpyrrolidone. U.S. Pat. No. 6,114,435discloses preparation of polymers containing N-vinylcarboxamide units.The N-vinylcarboxamide monomer includes N-vinylformamide,N-vinylmethylformamide, N-vinylacetamide, N-vinyl-N-methylacetamide,N-vinyl-N-ethylacetamide, N-vinylpropionamide,N-vinyl-N-methylpropionamide and N-vinylbutyramide. Followingpolymerization, hydrolysis leads to vinylamine polymers. U.S. Pat. No.6,057,404 discloses preparation of β-hydroxyalkylvinylamine polymers.U.S. Pat. No. 5,863,879 discloses preparation of N-substitutedvinylamine polymers wherein the substituent is C1-C6 alkyl. U.S. Pat.No. 5,280,077 discloses synthesis of oligomeric vinylamines havingmolecular weights in the range 600 to 2,500. The weight averagemolecular weight, M_(w), of the vinylamine polymer of the presentinvention may be 500 to 5,000,000, preferably 2,000 to 500,000, morepreferably 5,000 to 250,000, and most preferably 10,000 to 75,000.

The amount of vinylamine polymer useful in the present invention istypically 0.25 to 40 weight percent, preferably 0.5 to 30 weight %, morepreferably 1 to 20 weight %, and most preferably 2 to 10 weight %, basedon the weight of the binder polymer.

The type and amount of volatile base used must be sufficient to raisethe pH of the composition to about the point where the polyfunctionalamine is non-ionized (deprotonated), to avoid interaction with theanionically stabilized emulsion. The volatile base of preference isammonia, which may be used as the sole volatile base or in admixturewith other volatile or nonvolatile bases. Volatile bases useful in thepresent invention include, for example, ammonia, morpholine, the loweralkyl amines, 2-dimethylaminoethanol, N-methylmorpholine,ethylenediamine, and others.

It is generally desirable to have additional components added to thecoating composition to form the final formulation for coatingcompositions, including traffic paints, described herein. Theseadditional components include, for example, thickeners; rheologymodifiers; dyes; sequestering agents; biocides; dispersants; pigments,such as, titanium dioxide, organic pigments, carbon black; extenders,such as calcium carbonate, talc, clays, silicas and silicates; fillers,such as glass or polymeric microspheres, quartz and sand; anti-freezeagents; plasticizers; adhesion promoters such as silanes; coalescents;wetting agents; surfactants; slip additives; crosslinking agents;defoamers; colorants; tackifiers; waxes; preservatives; freeze/thawprotectors; corrosion inhibitors; and anti-flocculants. Duringapplication of the aqueous coating composition of the present inventionto the surface of a substrate, glass or polymeric microspheres, quartzand sand may be added as part of the that coating composition or as aseparate component applied to the surface in a separate stepsimultaneously with, before, or after the step of application of theaqueous coating composition.

During application of the aqueous coating composition of the presentinvention to the surface of a substrate, “absorbers” may be added as aseparate component applied to the surface in a separate stepsimultaneously with, before, or after the step of application of theaqueous coating composition. Used herein, the term “absorber” refers tothe general class of materials that includes hollow sphere polymer, ionexchange resin beads (e.g., in acid form, in base form, in salt form, inpartially neutralized form, or in mixed salt form), and absorbentinorganic compounds (e.g., inorganic superabsorbent gel, Sumica gel),including talc. Other “absorbers” useful in the present invention aremolecular sieves, non-porous carbonaceous materials, porous carbonaceousmaterials, and superabsorbent polymers (abbreviated SAP or SAPs herein).These absorber are capable of further increasing the drying rate of theaqueous coating compositions of the present invention.

The aqueous coating compositions of the present invention include, forexample, interior house paints, exterior house paints, automotivepaints, appliance paints, and traffic paints. The preferred use of theaqueous coating composition of the present invention is as a trafficpaint which can be applied to a roadway surface to form a roadwaymarking.

EXPERIMENTAL

Lupasol™ LU 321 is a high molecular weight poly(vinylamine) availablefrom BASF Corporation of Rensselaer, N.Y.

Molecular Weight Determination using Gel Permeation Chromatography (GPC)

Gel Permeation Chromatography, otherwise known as size exclusionchromatography, actually separates the members of a distribution ofpolymer chains according to their hydrodynamic size in solution ratherthan their molar mass. The system is then calibrated with standards ofknown molecular weight and composition to correlate elution time withmolecular weight. The techniques of GPC are discussed in detail inModern Size Exclusion Chromatography, W. W. Yau, J. J Kirkland, D. D.Bly; Wiley-Interscience, 1979, and in A Guide to MaterialsCharacterization and Chemical Analysis, J. P. Sibilia; VCH, 1988, p.81-84.

For example, the molecular weight information for a low molecular weightsample (e.g., 10,000) may be determined as follows: The sample (anaqueous emulsion containing low molecular weight particles) is dissolvedin THF at a concentration of approximately 0.1% weight sample per volumeTHF, and shaken for 6 hours, followed by filtration through a 0.45 μmPTFE (polytetrafluoroethylene) membrane filter. The analysis isperformed by injecting 100 μl of the above solution onto 3 columns,connected in sequence and held at 40° C. The three columns are: one eachof PL Gel 5 100, PL Gel 5 1,000, and PL Gel 5 10,000, all available fromPolymer Labs, Amherst, Mass. The mobile phase used is THF flowing at 1ml/min. Detection is via differential refractive index. The system iscalibrated with narrow polystyrene standards. PMMA-equivalent molecularweights for the sample are calculated via Mark-Houwink correction usingK=14.1×10⁻³ ml/g and a=0.70 for the polystyrene standards andK=10.4×10⁻³ ml/g and a=0.697 for the sample.

Dry Through Tests

Each test paint is applied to a 4″ (10.2 cm)×12″ (30.5 cm) glass panelusing a drawdown blade having a gap of 500μ, (20 mils).

After application of the coating, the panels are immediately placed in ahigh humidity test chamber supplied by Victor Associates, Inc. (Hatboro,Pa.), maintained at a relative humidity of 90%±3%. This test chamber isequipped with a certified hygrometer and temperature indicator, both ofwhich are fastened to the center of the rear wall of the test chamber toensure balanced measurement. The 90%±3% relative humidity is obtained byfilling the pan at the bottom of the completely closed test chamber witha 1 inch layer of water, equilibrating the chamber overnight (about 16hours) before testing (bringing the relative humidity inside the chamberto 100%), and then adjusting the size of the side port openings toachieve a relative humidity of 90%±3% within the chamber. Thetemperature inside the test chamber is 23° C. (74° F.).

The door of the test chamber is opened briefly at 5-minute intervals toevaluate the dry-through time for the paint test panel. Dry-through timeis defined as the time it takes for a wet paint film to reach a statesuch that the paint cannot be distorted with a 90° thumb twist when thethumb is touching the paint surface, but no pressure is being applied.During the early stages of drying, dry through is assessed by pushing asmall applicator stick through the surface of the film to the substrate,and then gauging the dryness of the coating in the lower layer bydragging the applicator stick along the substrate for a length ofapproximately 0.5 inch (˜1.27 cm). As it becomes clear that the coatingis approaching a dried through state, the panel is then removed from thebox at the appropriate time, and the aforementioned 90° thumb twist testis conducted.

EXAMPLE 1 Preparation of an Aqueous Coating Composition Containing aBinder Polymer, a Vinylamine Polymer and a Volatile Base

To a 5-liter reactor containing 1224.6 g deionized water (DI water)under a nitrogen atmosphere at 81° C., 4.7 g of sodium dodecylbenzenesulfonate (23% active), 67.7 g of monomer emulsion, disclosed in table Ibelow, 3.2 g of sodium carbonate dissolved in 60 g DI water and 3.2 gammonium persulfate dissolved in 50 g DI water are added with stirring.The remainder of the monomer emulsion No. 1 and a solution of 3.2 gammonium persulfate dissolved in 100 g DI water are gradually added overa period of 162 minutes. At the end of the feed, 50 g of DI water isadded to rinse the monomer emulsion feed line. After cooling to 60° C.,9.0 g of an aqueous solution of ferrous sulfate heptahydrate (0.15%),1.6 g t-butylhydroperoxide dissolve in 20 g DI water and 0.8 g of sodiumsulfoxylate formaldehyde didhydrate dissolved in 20 g DI water areadded. Ammonium hydroxide (28%) is added to raise the pH toapproximately 10.7 after which is added 180 g of poly(vinylamine)solution (12% by weight, based on the total weight of aqueous solution).The weight average molecular weight, Mw, of the binder polymer should be250,000 as determined by gel permeation chromatography.

TABLE I Composition of Monomer Emulsion No. 1 Ingredient Emulsion NoWeight in grams DI water 541.1 sodium dodecylbenzenesulfonate 19.7 (23percent by weight in water) butyl acrylate 1080.0 methyl methacrylate1051.9 methacrylic acid 28.1

COMPARATIVE EXAMPLE A Preparation of an Aqueous Coating CompositionContaining a Binder Polymer, a Volatile Base, but no Vinylamine Polymer

To a 5-liter reactor containing 1224.6 g deionized water (DI water)under a nitrogen atmosphere at 81° C., 4.7 g of sodium dodecylbenzenesulfonate (23% active), 67.7 g of monomer emulsion, disclosed in Table Iabove, 3.2 g of sodium carbonate dissolved in 60 g DI water and 3.2 gammonium persulfate dissolved in 50 g DI water are added with stirring.The remainder of the monomer emulsion No. 1 and a solution of 3.2 gammonium persulfate dissolved in 100 g DI water are gradually added overa period of 162 minutes. At the end of the feed, 50 g of DI water isadded to rinse the monomer emulsion feed line. After cooling to 60° C.,9.0 g of an aqueous solution of ferrous sulfate heptahydrate (0.15%),1.6 g t-butylhydroperoxide dissolve in 20 g DI water and 0.8 g of sodiumsulfoxylate formaldehyde didhydrate dissolved in 20 g DI water areadded. Ammonium hydroxide (10.5 g of a 28% aqueous solution) is added.The weight average molecular weight, Mw, of the binder polymer should be250,000 as determined by gel permeation chromatography.

EXAMPLE 2 Preparation of an Aqueous Coating Composition Containing aBinder Polymer, a Vinylamine Polymer and a Volatile Base

To a 5-liter reactor containing 1257.0 g deionized water (DI water)under a nitrogen atmosphere at 81° C., 4.7 g of sodium dodecylbenzenesulfonate (23% active), 67.7 g of monomer emulsion, disclosed in TableII below, 3.2 g of sodium carbonate dissolved in 60 g DI water and 3.2 gammonium persulfate dissolved in 50 g DI water are added with stirring.The remainder of the monomer emulsion No. 2 and a solution of 3.2 gammonium persulfate dissolved in 100 g DI water are gradually added overa period of 162 minutes. At the end of the feed, 50 g of DI water isadded to rinse the monomer emulsion feed line. After cooling to 60° C.,9.0 g of an aqueous solution of ferrous sulfate heptahydrate (0.15%),1.6 g t-butylhydroperoxide dissolve in 20 g DI water and 0.8 g of sodiumsulfoxylate formaldehyde dihydrate dissolved in 20 g DI water are added.Ammonium hydroxide (28%) is added to raise the pH to approximately 10.8after which is added 135 g of polyvinylamine solution (12%). The weightaverage molecular weight, Mw, of the binder polymer should be 40,000 asdetermined by gel permeation chromatography.

TABLE II Composition of Monomer Emulsion No. 2 Ingredient Emulsion NoWeight in grams DI water 541.1 sodium dodecylbenzenesulfonate 19.7 (23percent by weight in water) butyl acrylate 1080.0 methyl methacrylate1051.9 methacrylic acid 28.1 n-dodecyl mercaptan 32.4

COMPARATIVE EXAMPLE B Preparation of an Aqueous Coating CompositionContaining a Binder Polymer, a Volatile Base, but no Vinylamine Polymer

To a 5-liter reactor containing 1257.0 g deionized water (DI water)under a nitrogen atmosphere at 81° C., 4.7 g of sodium dodecylbenzenesulfonate (23% active), 67.7 g of monomer emulsion, disclosed in TableII above, 3.2 g of sodium carbonate dissolved in 60 g DI water and 3.2 gammonium persulfate dissolved in 50 g DI water are added with stirring.The remainder of the monomer emulsion No. 2 and a solution of 3.2 gammonium persulfate dissolved in 100 g DI water are gradually added overa period of 162 minutes. At the end of the feed, 50 g of DI water isadded to rinse the monomer emulsion feed line. After cooling to 60° C.,9.0 g of an aqueous solution of ferrous sulfate heptahydrate (0.15%),1.6 g t-butylhydroperoxide dissolve in 20 g DI water and 0.8 g of sodiumsulfoxylate formaldehyde dihydrate dissolved in 20 g DI water are added.Ammonium hydroxide (10.5 g of a 28% aqueous solution) is added. Theweight average molecular weight, Mw, of the binder polymer should be40,000 as determined by gel permeation chromatography.

EXAMPLES 3 and 4, and COMPARATIVE EXAMPLES C and D Preparation of Paintsfrom Aqueous Coating Composition

To examples 1 and 2, and comparative examples A and B, the followingcomponents are added in the order shown in Table III to prepare thepre-mixes for examples 3 and 4, and comparative examples C and D:

TABLE III Ingredients used to prepare pre-mixes for Examples 3 and 4 andComparative Examples C and D. Comp. Comp. Example 3 Example 4 Example CExample D Ingredient pre-mix pre-mix pre-mix pre-mix Example 1 433.3Example 2 433.3 Comparative 433.3 Example A Comparative 433.3 Example BDI water 20.7 20.7 20.7 20.7 Dispersant¹ 5.4 5.4 5.4 5.4 Surfactant² 2.92.9 2.9 2.9 Defoamer³ 2.1 2.1 2.1 2.1 White pigment⁴ 103.4 103.4 103.4103.4 Extender⁵ 786.5 786.5 786.5 786.5 Unless stated otherwise, thefollowing commercial components were used: ¹Tamol 901 Dispersant, anammonium salt of polyelectrolyte supplied by Rohm and Haas company,Philadelphia, PA @ 30% by weight ²Surfynol CT-136 Surfactant, anacetylenic surfactant supplied by Air Products and chemicals, Inc.,Allentown, PA ³Drew L-493 Defoamer supplied by Drew Chemical Company,Boonton, NJ ⁴Ti Pure R-900 Titanium dioxide supplied by E.I.duPont deNemours & Company, Wilmington, DE ⁵Omyacarb 5, Ground natural calciumcarbonate, evaluated under ASTM D 1199, Type GC, Grade 11 having anumber average particle size of 5.5 microns with maximum oil adsorptionNo. of 10, supplied by Omya, Inc., Proctor, VT

The components of Table III are mixed for 10 minutes or until smooth(the fineness of the grind as tested according to ASTM D1210 of not lessthan 3 Hegmen units) to form a mix to which the following components areadded, in the order shown in Table IV, with continuous mixing:

TABLE IV Ingredients used to prepare Examples 3 and 4 and ComparativeExamples C and D. Comp. Comp. Ingredient Example 3 Example 4 Example CExample D Example 3 pre-mix 1354.3 Example 4 pre-mix 1354.3 Comparative1354.3 Example C pre-mix Comparative 1354.3 Example D pre-mix methanol25.8 25.8 25.8 25.8 coalescing solvent⁶ 19.2 19.2 19.2 19.2 defoamer³3.6 3.6 3.6 3.6 unless otherwise noted the following commercialcomponents were used: ⁶Texanol Ester alcohol supplied by EastmanChemicals, Kingsport, TN ³Drew L-493 Defoamer supplied by Drew ChemicalCompany, Boonton, NJ

TABLE V Dry- through Empl. Paint Formulation Time^(a) Drawdown No.vinylamine polymer (from Table IV) (min.) gap 5 none Comparative >180 20mils Example C 6 none Comparative >180 20 mils Example D 7poly(vinylamine) Example 3 45 20 mils 8 poly(vinylamine) Example 4 45 20mils ^(a)Dry-through time was measured at 23° C. and 90% relativehumidity.

1. A method of producing a coating on the surface of a substrate, saidmethod comprising the steps of: (i) applying to said surface an aqueouscomposition comprising an anionically stabilized binder polymer; (ii)applying to said surface an aqueous composition comprising a vinylaminepolymer having from 20% to 100% by weight of amine functional units,based on total weight of said vinylamine polymer; and (iii) drying saidcoating.
 2. The method of claim 1, wherein said aqueous compositioncomprising a vinylamine polymer further comprises an amount of volatilebase sufficient to deprotonate 60% to 100% of the amine groups of saidvinylamine polymer; and wherein said method further comprises the stepof evaporating said volatile base from said coating.
 3. The method asclaimed in claim 2, wherein the said amount of volatile base issufficient to deprotonate essentially all of the amine groups of thesaid vinylarnine polymer.